OCR Text |
Show FIRST EXPERIMENTAL RESULTS - COMPARISON WITH THE CALCULATION Experiments are currently being carried out on a prototype of the immersion tube. Temperature and pressure will be measured at several points of flow. A comparison of the experimental results with the program for all the conditions under study above is therefore not possible. However, a measured value of the power transmi tted to the shell (Pt ) is available for P e = 53kH ; it is 35kW. For the same value of Pe' the program provides a value of Pt of 38kW, ie. an overestimation of about 10%. This result is too incomplete to permit discussion of the validity of the model and the modifications that may be required to improve its accuracy. However, it may be used to check that the order of magnitude of the heat transfers measured corresponds to that determined by the program. INITIAL CONCLUSIONS A numerical program for the determination of unsteady eddy flow and calculation of heat transfers (convective and radiative) wi thin the flow has been constructed. It will be used, after an indispensable phase of confrontation with the experimental results, to design (from an aerothermal point of view) new ranges of industrial equipment such as the immersion tube. The first results of the calculation-experimental comparison appear encouraging. At the same time, collaboration between the CNRS and GAZ DE FRANCE is continuing to develop the program through the integration of a turbulent combustion model for application to burners with separate air-gas supply. REFERENCES [1] D. DUTOYA - Une methode de volumes finis de type implici te pour Ie calcul des ecoulements elliptiques - La Recherche AerospatiaIe n02, 123-129 (1980). [2] F. DUPOIRIEUX Prediction d'ecoulements turbulents reactifs- AGARD PEP 62th meeting, Izmir, TURQUIE, oct. 1983 [3] F. DUPOIRIEUX, D. SCHERRER - Methodes numeriques a convergence rapide utilisees pour Ie calcul des ecoulements reactifs I.N.R.I.A., Sophia-Antipolis, FRANCE, mai 1985. [4] B. COURBET - Une methode de calcul des ecoulements turbulents tridimensionnels dans les diffuseurs - La Recherche Aerospatiale, nO 3, 155-165 (1984) [5] R. BORGHI, H. TOCHTINSKY, M.GONZALES - Physical aspects of numerical modelling of flows with combustion - I.N.R.I.A. 7th 134 International Conference on Computing Methods in Applied Science and Enginerring. [6] F. HIRSINGER - Modelisation en aerothermique instationnaire - La Recherche Aerospatiale nOS, 307-323 (1979). [7] R.M. BEAM, R.F. WARNING - An implicit factored scheme for the compressible NavierStockes equations A.I.A.A. Journal vol. 16, n04, 393-402 (1978). [ 8] A. G. DE MARCO, F. C. LOCKWOOD - A new flux model for calculation of radiation in furnaces - La Rivista dei Combustibili, 24, 5-6, 184 (1975). [9] H.C. HOTTEL, A.F. SARGOFIN Radiative Transfer Mc Graw Hill, New York U.S.A. [10] P.B. TAYLOR, P.J. FORSTER - The total emissivities of luminous and non-luminous flames - Int. J. Heat Mass Transfer nO vol. 17, 1591-1605 (1974). [11] R.M. DAVIES et al - The prediction of heat transfer and thermal performance in gasfired processes - 37th Autumn Research Meeting of the Institution of Gas Engineers, London, G-B (1971). APPENDIX : SYSTEM OF SYMBOLS USED x space co-ordinate t time p specific density u instantaneous velocity vector of combustion products u" fluctuation in turbulence of velocity vector of combustion products u average of velocity vector of combustion products (u = ij + u") T absolute temperature T" fluctuation in turbulence of temperature R ideal gas constant P pressure Cp specific heat at constant pressure of combustion products h enthalpy of combustion products ~" fluctuation in turbulence of enthalpy wR term representing radiation source ~t dynamic eddy viscosity k kinetic energy of the turbulence per unit of mass cr STEFAN number p' partial CO2+H20 pressure |